Abstract: Identifying program code similarity is to measure similar degree between codes with a kind of detection method, which is very important in the fields of computer science education and intellectual property protection. We introduced the research purpose, the history and some conceptual models of code similarity detection. By analyzing several approaches of code similarity detection, the characteristic of each method was summarized. hhen we discussed some code similarity based researches. Finally, the conclusion of the problems in current technologies was given before the discussion about some promising tendency of code similarity detection.

Key words: Code similarity, Automatic detection, Conceptual model